# How can I append to a vector in Octave?

When ever I have to append to a vector I am doing this.

A = [2 3 4] A = [A; 3 4 5]

I was wondering if there are any inbuilt functions for this or more elegant ways of doing this in Octave.

## Answers

The builtin functions are cat, vertcat, and horzcat, found on pages 380-381 of the Octave documentation (v 3.8). They are essentially equivalent to what you have though.

octave:5> A = [2 3 4]; octave:6> A = [A; 3 4 5] A = 2 3 4 3 4 5 octave:7> B = [4 5 6]; octave:8> B = vertcat(B,[5 6 7]) B = 4 5 6 5 6 7

Another (again equivalent) way would be to directly use matrix indexing (see page 132)

octave:9> C = [6 7 8]; octave:10> C(end+1,:) = [7 8 9] C = 6 7 8 7 8 9

I think that the most efficient is to use this built in function that you have posted in the question(I'm relying on other experts in octave i did not check it completely; The standard is that matrix operations are generally faster than iterative ones, I don't know what the inner mechanism that allows this to be enabled yet). Because a vector is a type of matrice, this solution will work for concatinating vectors (of any type) too:

vector = [vector ; value]